Installation for transporting and/or storing products sensitive to changes in temperature and humidity

ABSTRACT

The present invention relates to an installation for transporting and/or storing products sensitive to changes in temperature and humidity such as foodstuffs and in particular cocoa. The installation comprises a heat-insulated inner enclosure 1 containing such products and having upper and lower parts provided with openings 2, 3 to allow a surrounding gas such as air or a neutral gas to circulate through the inner enclosure. An outer enclosure surrounds the inner enclosure and is heat-insulated except for a portion of a its lower side walls. Means is provided for treating the circulating gas to reduce its relative humidity entering the inner enclosure to a value less than that of the gas-product equilibrium.

The invention has for its object a novel installation for transportingand/or storing products sensitive to changes in temperature andhumidity.

The present invention thus has two principal fields of application:storage and transport.

More precisely, the invention allows various storage installations to beproduced, such as for example silos, stores, warehouses, etc. andtransport installations such as for example large-dimensionedcontainers, bastard containers, crates, bags, cardboard boxes, packingcases, etc.

The products likely to be stored and/or transported, within theframework of the invention, are, on the one hand, powdery or granularproducts, such as in particular foodstuffs such as cocoa, and, on theother hand, any object or equipment sensitive to heat and demanding alimited hygrometry.

Within the particular domain of transport, the invention allows thetransport of a very extensive range of goods between two countries whoselocal temperatures are very different.

Up to the present time, the transport of tropical agricultural productsfrom producer countries with hot, damp climate towards consumercountries with temperate or cold climate, is inevitably accompanied byphysical phenomena of desorption, adsorption and condensation, i.e. oftransfer of humidity within the relatively closed volume constituted forexample by a container or crate.

These physical phenomena are the origin of serious deteriorations of theproducts transported.

Certain systems set up in specialized containers, such as naturalventilation, double partition, double floor, false ceiling, absorbentmaterial, etc. have been able to limit, slow down or delay the phenomenaof desorption, but none has given entire satisfaction nor enabled thedeteriorations in quality ascertained at arrival, particularly in thecase of cocoa, to be avoided.

It is an object of the present invention to overcome the drawbacks setforth hereinabove, by proposing an installation for transporting and/orstoring products sensitive to changes in temperature and humidity, ofnovel design, which makes it possible to avoid any degradation of theproducts even when the latter undergo, in time, considerable changes intemperature and/or humidity

The invention is based on the application of the following threeprinciples:

1. Regulate the heat transfers of the contents-container assembly, sothat the temperature of the contents always remains higher than thehumid temperature of the air (or of a neutral gas) in movement;

2. Use the movements of convection of the air (or a neutral gas) fortransporting the calories and humidity of the mass of the contentstowards a selected point of the container;

3. Reheat and dry the saturated air (or a neutral gas) before it comesinto contact again with the product, by means of a heat exchanger.

More precisely, the solution according to the invention, to solve thetechnical problem raised, consists in an installation for transportingand/or storing products sensitive to changes in temperature andhumidity, located in an environment of air or neutral gas undergoingmovements of convection resulting in particular from variations intemperature, such as in particular foodstuffs such as cocoa,characterized in that it comprises:

a heat-insulated inner enclosure 1 which contains said products, havingin its upper and lower parts at least one opening 2, 3 to allow air or aneutral surrounding gas to circulate through said inner enclosure 1;

an outer enclosure 5 surrounding said inner enclosure 1, which isheat-insulated with the exception of at least one part of its sidewalls, for example the lower part; and

means for treating the air or neutral gas circulating through the innerenclosure 1 in order to reduce the relative humidity of the air orneutral gas entering the inner enclosure, preferably to a value lessthan the relative humidity of the air-product equilibrium.

The present invention thus makes it possible, for the first time, tomaster and order the physical phenomena of air/product equilibrium,avoiding the reductions in quality of the stored or transported product.

According to a particular embodiment of the invention, these treatmentmeans comprise a heat exchanger.

According to another feature of the invention, the said heat exchangeris disposed on the path of circulation of the air or neutral gas, in thevicinity of the products, preferably in the lower part of said innerenclosure.

According to an advantageous embodiment of the invention, the said heatexchanger comprises an open cavity, preferably made inside theheat-insulated wall forming the bottom of the said inner enclosure, andopening out:

on the one hand, in its upper part in said inner enclosure, and

on the other hand, for example via channels, in the volume includedbetween said inner and outer enclosures.

This cavity is advantageously disposed substantially vertically withrespect to the upper opening of the inner enclosure, so as to create ashaft for the circulation of the air or neutral gas.

According to a particular feature of the invention, the said heatexchanger comprises in addition a removable partition for separationfrom the products contained in the inner enclosure, made for example inthe form of a grate possibly connected to a plate disposed at the bottomof said inner enclosure.

According to another advantageous feature of the invention, there may beprovided in said cavity and/or in the condensate recovery zone,materials which are absorbent, adsorbent and/or which reinforce thethermal mass of the exchanger or the condensate recovery zone, forexample steel wool.

This grate and this plate are advantageously made of a heat-conductingmaterial thus producing a thermal bridge between the inner volume of thesaid cavity and the inner enclosure.

The invention will be more readily understood and other purposes,characteristics and advantages thereof will appear more clearly onreading the following explanatory description, made with reference tothe accompanying schematic drawings given solely by way of non-limitingexamples, illustrating a presently preferred embodiment of the inventionand in which:

FIG. 1 is a view in principle in front section of an installationaccording to the present invention; and

FIG. 2 is a partial view thereof in perspective with parts torn away,illustrating the part forming the heat exchanger of this installation.

To clarify the demonstration, it has been chosen to describe theinvention within the particular framework of its application to thetransport of tropical agricultural products from producer products(sic.) with a hot, damp climate, to consumer countries with a coldclimate.

Naturally, it is question here only of a particular embodiment of theinvention intended to make the different physical phenomena coming intoplay, more readily understood.

Taking the example of a product such as a cocoa bean, the conditions ofair-product equilibrium at departure and at arrival make it possible tounderstand the transfers of humidity which are produced inside acontainer and the consequence thereof on the quality of the producttransported.

When the container is closed in the producer country, the water contentand the temperature of the product are generally homogeneous and theambient air is rapidly placed in equilibrium with the product withoutsignificant variation in its water content, even if this air has atemperature and a hygrometry different from the conditions ofequilibrium.

Alternations in humidity transfer, for example following a daily cycleincluding a night-time minimum and a day-time maximum, respectivelylower and higher than the humid temperature of the inner air (dew point)are tolerable and do not lead to loss of quality of the product.

On the contrary, during transport by sea, the outside temperaturedecreases progressively until it becomes permanently lower than thehumid temperature of the inner air.

The air-product equilibrium is thus broken and a considerableheterogeneity appears in the temperatures and the water contents of theproduct within its mass. In the case of cocoa, at the same time, moulddevelops and possibly heatings occur at certain spots.

Such phenomena are produced in any totally or partially closed volumeand may be observed in all types of presently existing containers. Inthe particular case of isothermal containers, it is upon opening of thedoors at arrival that these phenomena inevitably occur.

With reference to FIGS. 1 and 2, the specific arrangements of aninstallation according to the invention will now be described.

This installation comprises an inner enclosure 1 adapted to contain theproducts to be transported and/or stored. This enclosure 1 may be of anyshape and dimensions and they will be chosen as a function of the shapesand dimensions of the products to be transported and/or stored.

The inner enclosure 1 is heat-insulated for example by means ofinsulating panels known per se, and comprises at least one opening inits upper and lower parts, allowing the circulation of air (or possiblyof neutral gas) through the enclosure 1.

In the example shown, the enclosure 1 comprises an upper central opening2 and a plurality of lower lateral openings 3 which will be describedhereinafter.

This installation also comprises an outer enclosure 5 surrounding saidinner enclosure 1 which, in the example shown, has a generallyparallelepipedic form. The outer enclosure 5 is heat-insulated exceptfor at least one part, for example the low part "a" of its side walls.

Thus the inner wall of the enclosure 5 is heat-insulated along its upperhorizontal wall 6 and along the upper part 7 of its four vertical sidewalls.

Heat-insulation of the lower wall 8 of the enclosure 5 is ensured by thepanel insulating the bottom of the inner enclosure 1 which rests on thebottom 8 of the outer enclosure 5.

Finally, the installation according to the invention comprises a heatexchanger which will be disposed on the path of circulation of the airor the neutral gas in movement, in the vicinity of the products, forexample in the lower part of the inner enclosure 1.

In the presently preferred embodiment, this heat exchanger comprises anopen cavity 9 opening out, on the one hand, in its upper part in theinner enclosure 1 and, on the other hand, via channels joining theopenings 3, in the volume included between the inner (1) and outer (5)enclosures.

As shown in FIG. 2, the cavity 9 may be made in the form of a gutter,for example parallelepipedic, extending longitudinally in the medianpart of the inner enclosure 1, and communicating via an assembly ofchannels 12 extending parallel and transversely to said gutter, with thespace included between the inner (1) and outer (5) enclosures.

According to a preferred variant embodiment, the cavity 9 and thechannels 12 will be made in the panel insulating the bottom of the innerenclosure 1. The cavity 9 will preferably be disposed vertically,relatively to the opening 2, so as to create a "shaft" in which the airin movement will circulate.

This heat exchanger will comprise, in addition, a removable partition 10for separating from the products contained in the inner enclosure 1.This partition will for example be made in the form of a perforatedplate forming grate possibly connected to a plate 13 forming floor onwhich rest the products to be transported and/or stored. Thecavity-grate-floor assembly thus constitutes the heat exchanger.

Of course, other types of heat exchangers may be used in place of theone which has just been described. In particular, an exchanger may beimagined, constituted by a tube traversing the floor and embedded in themass of products to be transported and/or stored and of which the upperend is in the form of an upturned U, or any other type of exchanger.

Grates 14, 15 will advantageously be disposed at each end of thechannels 12, of which the shape of the fins (shown schematically inFIG. 1) will enable the possible drops of condensation to be guidedoutwardly of the cavity 9 at the level of the orifice opening out insaid cavity and outwardly at the level of the orifice opening out in thespace included between the inner (1) and outer (5) enclosures.

Thanks to the presence of the removable grate 10, the cavity 9 isaccessible by its upper part and products which are absorbent and/oradsorbent and/or of such nature as to increase the thermal mass of theexchanger, may for example be introduced.

The installation which has just been described functions as follows:When products are introduced in the inner enclosure 1, for example atthe port of embarcation where the temperature is relatively high (forexample 28° C.), the container-contents assembly goes into thermalequilibrium.

When the outside temperature decreases, the non-insulated part of thelateral walls cools the air which descends and moves in the directionindicated by the arrows.

When the outside temperature is lower than the dew point of the innerair, this inner air, whilst descending along the non-insulated part, issaturated, releasing water by condensation on the cold wall of the outerenclosure 5. The water of condensation trickles along this wall and iscollected in a condensate recovery zone 16 located at the bottom of theenclosure 5, between the lateral walls opposite the inner (1) and outer(5) enclosures. The saturated, relatively cold air (for example 17° to18° C.) enters the channels 12 via openings 3, then into cavity 9 whichthen acts as a heat exchanger since it is in direct vicinity of the massof the products and consequently at the same relatively high temperature(27°/28° C.).

Taking into account the considerable specific heat of the products, theair entering cavity 9 is heated (for example to a temperature of 23°/24°C.) and its relative humidity decreases to a value less than therelative humidity of air-product equilibrium (for example 65 to 70%).

The air then heats up in contact with the product (for example up to atemperature of 25° C.) whilst being laden with humidity (tendency toair-product equilibrium).

Having arrived in the upper part of the natural shaft formed in thevertical plane of symmetry of the inner enclosure 1, the air attains atemperature and relative humidity which are substantially equal to thoseof the product (for example a temperature of 25° to 26° C. and arelative humidity of about 75%).

The air having passed through the mass of products leaves through theupper opening 2 and moves in the free space located in the inner andouter enclosures; the natural convection movement represented in FIG. 1by arrows, being promoted by the cooling of the air located near thecold partition.

As will be understood, there is produced a cycle which progressivelycools and dries the cocoa, without the appearance of the condensationsand mould which are generally observed in the heretofore usedcontainers.

The homogeneity and progressivity of the cooling and desicccation areobtained by the regulation of the heat transfers and of the humiditytransfers.

Such regulation by convection results from the thermal and hydricexchange following from the specific conformation of the installationaccording to the invention.

To these transfers by convection are added transfers by conduction ofthe hottest zones towards the coldest zones of the mass, naturallyreinforcing the effects of homogeneity and of progressivity.

The advantages of the installation according to the invention aretherefore numerous.

In particular, the invention allows the transport and/or storage of awide range of products. These products may be transported equally wellin bags and in bulk, which makes it possible to benefit fully from theeconomical interest of the container.

The homogeneity and progressivity of the cooling and desiccationguarantee perfect conservation of the initial qualities and propertiesof the products.

It is obvious that the invention also covers a process for storingproducts affected by changes in temperature and/or humidity, such as inparticular foodstuffs, for example cocoa, contained in devices in whichsaid products are in an air or neutral gas environment undergoingmovements of convection resulting in particular from variations intemperature, characterized in that there are provided:

a heat-insulated inner enclosure 1 adapted to contain said products andcomprising in its upper and lower parts at least one opening 2, 3allowing the circulation of air or of neutral gas through saidenclosure;

an outer enclosure 5, surrounding said inner enclosure 1 and of whichthe inner wall is heat-insulated except for at least one part of itslateral walls, for example the lower part, and in that the air orneutral gas circulating through the products is treated so as to reducethe relative humidity of the air or neutral gas entering said innerenclosure, preferably to a value less than the relative humidity of theair-product equilibrium.

As will be understood, the present invention is based on a static heatexchange between a product contained in a partially or totally closedvolume and the interstitial ambient gas (possibly air).

One of the originalities of the invention is that no mechanical meansare used for controlling the temperature and/or hygrometric degree of agas, but that a static heat exchanger is used.

I claim:
 1. Installation for transporting and/or storing productssensitive to changes in temperature and humidity, located in anenvironment of a gas selected from the group consisting of air andneutral gas undergoing movements of convection resulting from variationsin temperature, characterized in that the installation comprises:aheat-insulated inner enclosure which contains said products, and havingupper and lower parts wherein each of the upper and lower parts of saidinner enclosure is provided with at least one opening to allowsurrounding gas to circulate through said inner enclosure; an outerenclosure having an upper and a lower part surrounding and spaced fromsaid inner enclosure and heat-insulated with the exception of at least aportion of the lower part of said outer enclosure, whereby the inner andouter enclosures define an open space for free circulation of gastherebetween; and means for treating the circulating gas in order toreduce the relative humidity or the gas entering the inner enclosure toa value less than the relative humidity of the gas-product equilibrium.2. Installation according to claim 1, characterized in that the saidtreatment means comprise a heat exchanger.
 3. Installation according toclaim 2, characterized in that said heat exchanger is disposed in thepath of circulation of the gas, in the vicinity of the products, in thelower part of said inner enclosure.
 4. Installation according to claim 2and located in an environment of air or neutral gas undergoing movementof convection resulting in particular from variations in temperature,characterized in that said heat exchanger comprises an open cavityinside a heat-insulated wall forming a bottom of said inner enclosure,and wherein an upper side of the cavity communicates with said innerenclosure, and a lower side of the cavity communicates, via channelswith a space between said inner and outer enclosures.
 5. Installationaccording to claim 4, characterized in that said open cavity is disposedin substantially vertical alignment with respect to the upper opening ofthe inner enclosure, so as to create a shaft for the circulation of thegas.
 6. Installation according to claim 4, characterized in that saidheat exchanger comprises a removable partition for separation of theproducts contained in the inner enclosure from the open cavity, saidpartition being in the form of a perforated grate disposed over theupper side of the open cavity.
 7. Installation according to claim 5,characterized in that said heat exchanger comprises a removablepartition for separation of the products contained in the innerenclosure from the open cavity, said partition being in the form of aperforated grate disposed over the upper side of the open cavity. 8.Installation according to claim 6, further comprising a plate disposedat the bottom of said inner enclosure, having an aperture correspondingto said open cavity, and forming a floor of said inner enclosure, andwherein said grate is connected to said plate about the periphery ofsaid open cavity.
 9. Installation according to claim 8, characterized inthat the grate and the plate are made of a heat-conducting material thusproducing a thermal bridge between the inner volume of said cavity andthe inner enclosure.
 10. Installation according to claim 7, furthercomprising a plate disposed at the bottom of said inner enclosure,having an aperture corresponding to said open cavity, and forming afloor of said inner enclosure, and wherein said grate is connected tosaid plate about the periphery of said open cavity.
 11. Installationaccording to claim 4, wherein a lowermost portion of the space betweenthe inner enclosure and the outer enclosure forms a condensate recoveryzone.
 12. Installation according to claim 11, wherein there is disposedin said cavity and/or in the condensate recovery zone a materialselected from the group of materials which are moisture adsorbents,moisture adsorbents, and materials which reinforce the thermal mass ofsaid heat exchanger and/or the condensate recovery zone.